(a) Technical Field
The present invention relates to a method for assembling a fuel cell stack of a fuel cell vehicle by using a fixing block and a fixing pin and a fuel cell stack therefrom, which can reduce the time and process required for assembling the fuel cell stack and facilitate mass production.
(b) Background Art
A fuel cell system generates electricity by electrochemically converting chemical energy into electric energy rather than converting the chemical energy into heat via combustion.
The fuel cell system typically comprises the fuel cell stack for generating electricity, a hydrogen supply system for supplying hydrogen as a fuel to the fuel cell stack, an air (oxygen) supply system for supplying oxygen in the air, which is an oxidizing agent required for an electrochemical reaction, to the fuel cell stack, and a thermal management system (TMS) for removing reaction heat of the fuel cell stack to the outside of the fuel cell system, controlling the operation temperature of the fuel cell stack, and performing water management function.
In the above-described fuel cell system, the fuel cell stack is a device that generates electricity by reacting hydrogen as a fuel and oxygen in the air.
As shown in FIG. 10, a unit cell 100 of the fuel cell stack includes a membrane electrode assembly 101 (MEA), a gas diffusion layer 102 (GDL), a separator 103, and a gasket 104 for maintaining airtightness. The unit cell generates electricity by a chemical reaction represented by the following formula 1:Anode: H2→2H++2e−Cathode: ½O2+2H++2e−→H2O  [Formula 1]
Through the above reaction, the unit cell 100 generates electricity ranging from 0.6 to 1.0V, about 0.7V on the average.
Since the fuel cell stack for a vehicle requires a high power, at least about 400 unit cells are piled together in a fuel cell stack to obtain a desired voltage.
Conventionally, the unit cells are stacked in series in the fuel cell stack by, for example, fixing end plates 106, positioned on both ends of stacked cells, using a long bolt 105 as shown in FIG. 11, fixing end plates 106 by bolting a fastening bar 107 or a fastening plate thereto as shown in FIG. 12, or putting a fastening bar 108 around the whole circumference of the fuel cell stack as shown in FIG. 13.
In particular, U.S. Pat. Nos. 6,455,179 and 4,345,009, Japanese Patent No. 2004-0065492 disclose methods of assembling a fuel cell stack using a long bolt and a nut. However, the methods are time-consuming, especially with respect to the bolt connection and thus is not suitable for automated process.
Also, Japanese Patent Nos. 2006-54067, 2006-66256, 2006-73226, and 2006-73459 disclose methods of assembling end plates to a fuel cell stack by inserting a pin into a tab provided on the end plates and the bottom, top and side plates. However, the methods have a drawback in that the pins may be escaped from their own position by vibration or shock.
Additionally, U.S. Pat. No. 6,645,659 discloses a method of assembling a fuel cell stack by coupling end plates to a tension plate by a serration and a bolt. However, the method is time-consuming in bolting process.
In addition, U.S. Pat. No. 5,789,901 discloses a method of assembling a fuel cell stack using a fastening band and a disc spring. However, the method requires a high pressure device since it involves a high load during fastening process. In a case where the whole fuel cell stack is wrapped by a fastening band, this method is not feasible.
The conventional methods use a great number of bolts during assembly, a lot of time is taken to perform the bolting process and a number of processes are required. As a result, the methods are disadvantageous for mass production.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.